Reminds me of the evergreen Joseph Heller anecdote:
"At a party given by a billionaire on Shelter Island, Kurt Vonnegut informs his pal, Joseph Heller, that their host, a hedge fund manager, had made more money in a single day than Heller had earned from his wildly popular novel Catch 22 over its whole history. Heller responds, 'Yes, but I have something he will never have . . . Enough.'"
For a virus, the average number of people a sick person infects. If r < 1, the spread is self-limiting. If r > 1, it spreads exponentially until r drops (because, say, enough people develop immunity).
"At a party given by a billionaire on Shelter Island, Kurt Vonnegut informs his pal, Joseph Heller, that their host, a hedge fund manager, had made more money in a single day than Heller had earned from his wildly popular novel Catch 22 over its whole history. Heller responds, 'Yes, but I have something he will never have . . . Enough.'"